I. Components of the High Voltage Circuit Breaker Breaker Terminal Voltage Test Device
(1) High Voltage Boost Unit
The power frequency test transformer is mainly divided into three types: oil-immersed, gas-filled (SF6), and dry type. For high voltage levels of 110kV and above, a series excitation structure is generally used, achieving higher output voltage through the connection of multiple transformers in series.
The resonant reactor belongs to a series resonant device. It can be used for capacitive loads such as the circuit breaker breaker terminals. By using the inductance and the test specimen capacitance to form series resonance, high voltage can be generated. The required power supply capacity is only 1/5 to 1/10 of the traditional power frequency test, and the equipment is lighter and more portable.
(2) Voltage Regulation and Frequency Control Unit
Contact-type voltage regulators are mostly used in traditional power frequency withstand voltage instruments and have the characteristics of large volume and prone to carbon brush wear.
The frequency power supply is used in conjunction with the resonant reactor, which can convert the power frequency current into adjustable AC current with a frequency of 30–300Hz. By adjusting the frequency, the test circuit can enter the resonant state, with advantages of complete protection function and excellent output waveform quality.
(3) Measurement and Protection Module
The capacitor divider can monitor the high-voltage terminal voltage in real time and send the voltage signal to the control system.
The protection resistor includes water resistors and winding resistors, which are connected in series to the high-voltage output terminal. It can limit the short-circuit current when the specimen breaks down and prevent damage to the equipment winding.
The discharge device includes automatic discharge rods and grounding switches. It can automatically or manually discharge the high-voltage part to ground after the test, ensuring the safety of the test operation.
(4) Auxiliary Accessories
The shielding wire is used to connect the measuring instrument to reduce the power frequency interference in the high-voltage environment and ensure the accuracy of the test data.
The equalizing hood is suitable for 110kV and above circuit breaker tests and is installed at the end of the high-voltage lead-out line. It can eliminate the influence of corona discharge on the test results.
II. Detailed Selection Guide for Voltage Test Devices
The selection of voltage test devices should be determined based on the type of the tested item, the on-site power supply conditions, and the test purpose. It cannot be determined solely based on the voltage level.
(1) Voltage Level Matching
The rated output voltage of the device should be higher than the test voltage standard of the circuit breaker breaker terminals. The test voltage is usually a multiple of the equipment’s rated voltage. Specific values can be referred to relevant standards. For example, the test voltage of a 252kV circuit breaker breaker terminal can reach 460kV, and a 500kV-level device needs to be selected.
(2) Capacity Calculation
The capacity of the device depends on the capacitance between the circuit breaker breaker terminals, including equalizing capacitance and breaker terminal capacitance. The larger the capacitance, the higher the required test transformer capacity.
For oil-filled or vacuum circuit breakers, the capacitance is small, and a conventional power frequency test transformer can be selected; for SF6 circuit breakers, especially GIS equipment, the capacitance is large, and it is recommended to use a resonant device to reduce the requirements for power supply capacity.
(3) Functionality Requirements Adaptation
Batch tests on-site can use an intelligent integrated machine; for research and development or factory tests, it is recommended to use high-precision split-type devices or resonant devices; for on-site emergency repairs or scenarios with limited working space, portable or lightweight gas-filled test transformers are suitable.
(4) On-site Power Supply Conditions
Devices with a capacity of 5kVA or less can use a 220V single-phase power supply; devices with a capacity of 10kVA or more or resonant devices need to use a 380V power input. Before selection, the on-site power supply system should be confirmed.
(5) Special Breaker Terminal Types
When testing double-breaker or multi-breaker circuit breakers, it is necessary to consider whether the device can handle the uneven breakdown voltage during the test process. It can also be combined with dedicated test cables or equalizing resistors to achieve synchronous voltage application.
Post time: Mar-04-2026